/*
	Public domain by Andrew M. <liquidsun@gmail.com>
	See: https://github.com/floodyberry/curve25519-donna

	32 bit integer curve25519 implementation
*/

#include "ed25519_donna.h"

static const uint32_t reduce_mask_25 = (1 << 25) - 1;
static const uint32_t reduce_mask_26 = (1 << 26) - 1;

/* out = in */
void curve25519_copy(bignum25519 out, const bignum25519 in) {
    out[0] = in[0];
    out[1] = in[1];
    out[2] = in[2];
    out[3] = in[3];
    out[4] = in[4];
    out[5] = in[5];
    out[6] = in[6];
    out[7] = in[7];
    out[8] = in[8];
    out[9] = in[9];
}

/* out = a + b */
void curve25519_add(bignum25519 out, const bignum25519 a, const bignum25519 b) {
    out[0] = a[0] + b[0];
    out[1] = a[1] + b[1];
    out[2] = a[2] + b[2];
    out[3] = a[3] + b[3];
    out[4] = a[4] + b[4];
    out[5] = a[5] + b[5];
    out[6] = a[6] + b[6];
    out[7] = a[7] + b[7];
    out[8] = a[8] + b[8];
    out[9] = a[9] + b[9];
}

void curve25519_add_after_basic(bignum25519 out, const bignum25519 a, const bignum25519 b) {
    uint32_t c = 0;
    out[0] = a[0] + b[0];
    c = (out[0] >> 26);
    out[0] &= reduce_mask_26;
    out[1] = a[1] + b[1] + c;
    c = (out[1] >> 25);
    out[1] &= reduce_mask_25;
    out[2] = a[2] + b[2] + c;
    c = (out[2] >> 26);
    out[2] &= reduce_mask_26;
    out[3] = a[3] + b[3] + c;
    c = (out[3] >> 25);
    out[3] &= reduce_mask_25;
    out[4] = a[4] + b[4] + c;
    c = (out[4] >> 26);
    out[4] &= reduce_mask_26;
    out[5] = a[5] + b[5] + c;
    c = (out[5] >> 25);
    out[5] &= reduce_mask_25;
    out[6] = a[6] + b[6] + c;
    c = (out[6] >> 26);
    out[6] &= reduce_mask_26;
    out[7] = a[7] + b[7] + c;
    c = (out[7] >> 25);
    out[7] &= reduce_mask_25;
    out[8] = a[8] + b[8] + c;
    c = (out[8] >> 26);
    out[8] &= reduce_mask_26;
    out[9] = a[9] + b[9] + c;
    c = (out[9] >> 25);
    out[9] &= reduce_mask_25;
    out[0] += 19 * c;
}

void curve25519_add_reduce(bignum25519 out, const bignum25519 a, const bignum25519 b) {
    uint32_t c = 0;
    out[0] = a[0] + b[0];
    c = (out[0] >> 26);
    out[0] &= reduce_mask_26;
    out[1] = a[1] + b[1] + c;
    c = (out[1] >> 25);
    out[1] &= reduce_mask_25;
    out[2] = a[2] + b[2] + c;
    c = (out[2] >> 26);
    out[2] &= reduce_mask_26;
    out[3] = a[3] + b[3] + c;
    c = (out[3] >> 25);
    out[3] &= reduce_mask_25;
    out[4] = a[4] + b[4] + c;
    c = (out[4] >> 26);
    out[4] &= reduce_mask_26;
    out[5] = a[5] + b[5] + c;
    c = (out[5] >> 25);
    out[5] &= reduce_mask_25;
    out[6] = a[6] + b[6] + c;
    c = (out[6] >> 26);
    out[6] &= reduce_mask_26;
    out[7] = a[7] + b[7] + c;
    c = (out[7] >> 25);
    out[7] &= reduce_mask_25;
    out[8] = a[8] + b[8] + c;
    c = (out[8] >> 26);
    out[8] &= reduce_mask_26;
    out[9] = a[9] + b[9] + c;
    c = (out[9] >> 25);
    out[9] &= reduce_mask_25;
    out[0] += 19 * c;
}

/* multiples of p */
static const uint32_t twoP0 = 0x07ffffda;
static const uint32_t twoP13579 = 0x03fffffe;
static const uint32_t twoP2468 = 0x07fffffe;
static const uint32_t fourP0 = 0x0fffffb4;
static const uint32_t fourP13579 = 0x07fffffc;
static const uint32_t fourP2468 = 0x0ffffffc;

/* out = a - b */
void curve25519_sub(bignum25519 out, const bignum25519 a, const bignum25519 b) {
    uint32_t c = 0;
    out[0] = twoP0 + a[0] - b[0];
    c = (out[0] >> 26);
    out[0] &= reduce_mask_26;
    out[1] = twoP13579 + a[1] - b[1] + c;
    c = (out[1] >> 25);
    out[1] &= reduce_mask_25;
    out[2] = twoP2468 + a[2] - b[2] + c;
    c = (out[2] >> 26);
    out[2] &= reduce_mask_26;
    out[3] = twoP13579 + a[3] - b[3] + c;
    c = (out[3] >> 25);
    out[3] &= reduce_mask_25;
    out[4] = twoP2468 + a[4] - b[4] + c;
    out[5] = twoP13579 + a[5] - b[5];
    out[6] = twoP2468 + a[6] - b[6];
    out[7] = twoP13579 + a[7] - b[7];
    out[8] = twoP2468 + a[8] - b[8];
    out[9] = twoP13579 + a[9] - b[9];
}

/* out = in * scalar */
void curve25519_scalar_product(bignum25519 out, const bignum25519 in, const uint32_t scalar) {
    uint64_t a = 0;
    uint32_t c = 0;
    a = mul32x32_64(in[0], scalar);
    out[0] = (uint32_t)a & reduce_mask_26;
    c = (uint32_t)(a >> 26);
    a = mul32x32_64(in[1], scalar) + c;
    out[1] = (uint32_t)a & reduce_mask_25;
    c = (uint32_t)(a >> 25);
    a = mul32x32_64(in[2], scalar) + c;
    out[2] = (uint32_t)a & reduce_mask_26;
    c = (uint32_t)(a >> 26);
    a = mul32x32_64(in[3], scalar) + c;
    out[3] = (uint32_t)a & reduce_mask_25;
    c = (uint32_t)(a >> 25);
    a = mul32x32_64(in[4], scalar) + c;
    out[4] = (uint32_t)a & reduce_mask_26;
    c = (uint32_t)(a >> 26);
    a = mul32x32_64(in[5], scalar) + c;
    out[5] = (uint32_t)a & reduce_mask_25;
    c = (uint32_t)(a >> 25);
    a = mul32x32_64(in[6], scalar) + c;
    out[6] = (uint32_t)a & reduce_mask_26;
    c = (uint32_t)(a >> 26);
    a = mul32x32_64(in[7], scalar) + c;
    out[7] = (uint32_t)a & reduce_mask_25;
    c = (uint32_t)(a >> 25);
    a = mul32x32_64(in[8], scalar) + c;
    out[8] = (uint32_t)a & reduce_mask_26;
    c = (uint32_t)(a >> 26);
    a = mul32x32_64(in[9], scalar) + c;
    out[9] = (uint32_t)a & reduce_mask_25;
    c = (uint32_t)(a >> 25);
    out[0] += c * 19;
}

/* out = a - b, where a is the result of a basic op (add,sub) */
void curve25519_sub_after_basic(bignum25519 out, const bignum25519 a, const bignum25519 b) {
    uint32_t c = 0;
    out[0] = fourP0 + a[0] - b[0];
    c = (out[0] >> 26);
    out[0] &= reduce_mask_26;
    out[1] = fourP13579 + a[1] - b[1] + c;
    c = (out[1] >> 25);
    out[1] &= reduce_mask_25;
    out[2] = fourP2468 + a[2] - b[2] + c;
    c = (out[2] >> 26);
    out[2] &= reduce_mask_26;
    out[3] = fourP13579 + a[3] - b[3] + c;
    c = (out[3] >> 25);
    out[3] &= reduce_mask_25;
    out[4] = fourP2468 + a[4] - b[4] + c;
    c = (out[4] >> 26);
    out[4] &= reduce_mask_26;
    out[5] = fourP13579 + a[5] - b[5] + c;
    c = (out[5] >> 25);
    out[5] &= reduce_mask_25;
    out[6] = fourP2468 + a[6] - b[6] + c;
    c = (out[6] >> 26);
    out[6] &= reduce_mask_26;
    out[7] = fourP13579 + a[7] - b[7] + c;
    c = (out[7] >> 25);
    out[7] &= reduce_mask_25;
    out[8] = fourP2468 + a[8] - b[8] + c;
    c = (out[8] >> 26);
    out[8] &= reduce_mask_26;
    out[9] = fourP13579 + a[9] - b[9] + c;
    c = (out[9] >> 25);
    out[9] &= reduce_mask_25;
    out[0] += 19 * c;
}

void curve25519_sub_reduce(bignum25519 out, const bignum25519 a, const bignum25519 b) {
    uint32_t c = 0;
    out[0] = fourP0 + a[0] - b[0];
    c = (out[0] >> 26);
    out[0] &= reduce_mask_26;
    out[1] = fourP13579 + a[1] - b[1] + c;
    c = (out[1] >> 25);
    out[1] &= reduce_mask_25;
    out[2] = fourP2468 + a[2] - b[2] + c;
    c = (out[2] >> 26);
    out[2] &= reduce_mask_26;
    out[3] = fourP13579 + a[3] - b[3] + c;
    c = (out[3] >> 25);
    out[3] &= reduce_mask_25;
    out[4] = fourP2468 + a[4] - b[4] + c;
    c = (out[4] >> 26);
    out[4] &= reduce_mask_26;
    out[5] = fourP13579 + a[5] - b[5] + c;
    c = (out[5] >> 25);
    out[5] &= reduce_mask_25;
    out[6] = fourP2468 + a[6] - b[6] + c;
    c = (out[6] >> 26);
    out[6] &= reduce_mask_26;
    out[7] = fourP13579 + a[7] - b[7] + c;
    c = (out[7] >> 25);
    out[7] &= reduce_mask_25;
    out[8] = fourP2468 + a[8] - b[8] + c;
    c = (out[8] >> 26);
    out[8] &= reduce_mask_26;
    out[9] = fourP13579 + a[9] - b[9] + c;
    c = (out[9] >> 25);
    out[9] &= reduce_mask_25;
    out[0] += 19 * c;
}

/* out = -a */
void curve25519_neg(bignum25519 out, const bignum25519 a) {
    uint32_t c = 0;
    out[0] = twoP0 - a[0];
    c = (out[0] >> 26);
    out[0] &= reduce_mask_26;
    out[1] = twoP13579 - a[1] + c;
    c = (out[1] >> 25);
    out[1] &= reduce_mask_25;
    out[2] = twoP2468 - a[2] + c;
    c = (out[2] >> 26);
    out[2] &= reduce_mask_26;
    out[3] = twoP13579 - a[3] + c;
    c = (out[3] >> 25);
    out[3] &= reduce_mask_25;
    out[4] = twoP2468 - a[4] + c;
    c = (out[4] >> 26);
    out[4] &= reduce_mask_26;
    out[5] = twoP13579 - a[5] + c;
    c = (out[5] >> 25);
    out[5] &= reduce_mask_25;
    out[6] = twoP2468 - a[6] + c;
    c = (out[6] >> 26);
    out[6] &= reduce_mask_26;
    out[7] = twoP13579 - a[7] + c;
    c = (out[7] >> 25);
    out[7] &= reduce_mask_25;
    out[8] = twoP2468 - a[8] + c;
    c = (out[8] >> 26);
    out[8] &= reduce_mask_26;
    out[9] = twoP13579 - a[9] + c;
    c = (out[9] >> 25);
    out[9] &= reduce_mask_25;
    out[0] += 19 * c;
}

/* out = a * b */
#define curve25519_mul_noinline curve25519_mul
void curve25519_mul(bignum25519 out, const bignum25519 a, const bignum25519 b) {
    uint32_t r0 = 0, r1 = 0, r2 = 0, r3 = 0, r4 = 0, r5 = 0, r6 = 0, r7 = 0, r8 = 0, r9 = 0;
    uint32_t s0 = 0, s1 = 0, s2 = 0, s3 = 0, s4 = 0, s5 = 0, s6 = 0, s7 = 0, s8 = 0, s9 = 0;
    uint64_t m0 = 0, m1 = 0, m2 = 0, m3 = 0, m4 = 0, m5 = 0, m6 = 0, m7 = 0, m8 = 0, m9 = 0, c = 0;
    uint32_t p = 0;

    r0 = b[0];
    r1 = b[1];
    r2 = b[2];
    r3 = b[3];
    r4 = b[4];
    r5 = b[5];
    r6 = b[6];
    r7 = b[7];
    r8 = b[8];
    r9 = b[9];

    s0 = a[0];
    s1 = a[1];
    s2 = a[2];
    s3 = a[3];
    s4 = a[4];
    s5 = a[5];
    s6 = a[6];
    s7 = a[7];
    s8 = a[8];
    s9 = a[9];

    m1 = mul32x32_64(r0, s1) + mul32x32_64(r1, s0);
    m3 = mul32x32_64(r0, s3) + mul32x32_64(r1, s2) + mul32x32_64(r2, s1) + mul32x32_64(r3, s0);
    m5 = mul32x32_64(r0, s5) + mul32x32_64(r1, s4) + mul32x32_64(r2, s3) + mul32x32_64(r3, s2) +
         mul32x32_64(r4, s1) + mul32x32_64(r5, s0);
    m7 = mul32x32_64(r0, s7) + mul32x32_64(r1, s6) + mul32x32_64(r2, s5) + mul32x32_64(r3, s4) +
         mul32x32_64(r4, s3) + mul32x32_64(r5, s2) + mul32x32_64(r6, s1) + mul32x32_64(r7, s0);
    m9 = mul32x32_64(r0, s9) + mul32x32_64(r1, s8) + mul32x32_64(r2, s7) + mul32x32_64(r3, s6) +
         mul32x32_64(r4, s5) + mul32x32_64(r5, s4) + mul32x32_64(r6, s3) + mul32x32_64(r7, s2) +
         mul32x32_64(r8, s1) + mul32x32_64(r9, s0);

    r1 *= 2;
    r3 *= 2;
    r5 *= 2;
    r7 *= 2;

    m0 = mul32x32_64(r0, s0);
    m2 = mul32x32_64(r0, s2) + mul32x32_64(r1, s1) + mul32x32_64(r2, s0);
    m4 = mul32x32_64(r0, s4) + mul32x32_64(r1, s3) + mul32x32_64(r2, s2) + mul32x32_64(r3, s1) +
         mul32x32_64(r4, s0);
    m6 = mul32x32_64(r0, s6) + mul32x32_64(r1, s5) + mul32x32_64(r2, s4) + mul32x32_64(r3, s3) +
         mul32x32_64(r4, s2) + mul32x32_64(r5, s1) + mul32x32_64(r6, s0);
    m8 = mul32x32_64(r0, s8) + mul32x32_64(r1, s7) + mul32x32_64(r2, s6) + mul32x32_64(r3, s5) +
         mul32x32_64(r4, s4) + mul32x32_64(r5, s3) + mul32x32_64(r6, s2) + mul32x32_64(r7, s1) +
         mul32x32_64(r8, s0);

    r1 *= 19;
    r2 *= 19;
    r3 = (r3 / 2) * 19;
    r4 *= 19;
    r5 = (r5 / 2) * 19;
    r6 *= 19;
    r7 = (r7 / 2) * 19;
    r8 *= 19;
    r9 *= 19;

    m1 +=
        (mul32x32_64(r9, s2) + mul32x32_64(r8, s3) + mul32x32_64(r7, s4) + mul32x32_64(r6, s5) +
         mul32x32_64(r5, s6) + mul32x32_64(r4, s7) + mul32x32_64(r3, s8) + mul32x32_64(r2, s9));
    m3 +=
        (mul32x32_64(r9, s4) + mul32x32_64(r8, s5) + mul32x32_64(r7, s6) + mul32x32_64(r6, s7) +
         mul32x32_64(r5, s8) + mul32x32_64(r4, s9));
    m5 += (mul32x32_64(r9, s6) + mul32x32_64(r8, s7) + mul32x32_64(r7, s8) + mul32x32_64(r6, s9));
    m7 += (mul32x32_64(r9, s8) + mul32x32_64(r8, s9));

    r3 *= 2;
    r5 *= 2;
    r7 *= 2;
    r9 *= 2;

    m0 +=
        (mul32x32_64(r9, s1) + mul32x32_64(r8, s2) + mul32x32_64(r7, s3) + mul32x32_64(r6, s4) +
         mul32x32_64(r5, s5) + mul32x32_64(r4, s6) + mul32x32_64(r3, s7) + mul32x32_64(r2, s8) +
         mul32x32_64(r1, s9));
    m2 +=
        (mul32x32_64(r9, s3) + mul32x32_64(r8, s4) + mul32x32_64(r7, s5) + mul32x32_64(r6, s6) +
         mul32x32_64(r5, s7) + mul32x32_64(r4, s8) + mul32x32_64(r3, s9));
    m4 +=
        (mul32x32_64(r9, s5) + mul32x32_64(r8, s6) + mul32x32_64(r7, s7) + mul32x32_64(r6, s8) +
         mul32x32_64(r5, s9));
    m6 += (mul32x32_64(r9, s7) + mul32x32_64(r8, s8) + mul32x32_64(r7, s9));
    m8 += (mul32x32_64(r9, s9));

    r0 = (uint32_t)m0 & reduce_mask_26;
    c = (m0 >> 26);
    m1 += c;
    r1 = (uint32_t)m1 & reduce_mask_25;
    c = (m1 >> 25);
    m2 += c;
    r2 = (uint32_t)m2 & reduce_mask_26;
    c = (m2 >> 26);
    m3 += c;
    r3 = (uint32_t)m3 & reduce_mask_25;
    c = (m3 >> 25);
    m4 += c;
    r4 = (uint32_t)m4 & reduce_mask_26;
    c = (m4 >> 26);
    m5 += c;
    r5 = (uint32_t)m5 & reduce_mask_25;
    c = (m5 >> 25);
    m6 += c;
    r6 = (uint32_t)m6 & reduce_mask_26;
    c = (m6 >> 26);
    m7 += c;
    r7 = (uint32_t)m7 & reduce_mask_25;
    c = (m7 >> 25);
    m8 += c;
    r8 = (uint32_t)m8 & reduce_mask_26;
    c = (m8 >> 26);
    m9 += c;
    r9 = (uint32_t)m9 & reduce_mask_25;
    p = (uint32_t)(m9 >> 25);
    m0 = r0 + mul32x32_64(p, 19);
    r0 = (uint32_t)m0 & reduce_mask_26;
    p = (uint32_t)(m0 >> 26);
    r1 += p;

    out[0] = r0;
    out[1] = r1;
    out[2] = r2;
    out[3] = r3;
    out[4] = r4;
    out[5] = r5;
    out[6] = r6;
    out[7] = r7;
    out[8] = r8;
    out[9] = r9;
}

/* out = in * in */
void curve25519_square(bignum25519 out, const bignum25519 in) {
    uint32_t r0 = 0, r1 = 0, r2 = 0, r3 = 0, r4 = 0, r5 = 0, r6 = 0, r7 = 0, r8 = 0, r9 = 0;
    uint32_t d6 = 0, d7 = 0, d8 = 0, d9 = 0;
    uint64_t m0 = 0, m1 = 0, m2 = 0, m3 = 0, m4 = 0, m5 = 0, m6 = 0, m7 = 0, m8 = 0, m9 = 0, c = 0;
    uint32_t p = 0;

    r0 = in[0];
    r1 = in[1];
    r2 = in[2];
    r3 = in[3];
    r4 = in[4];
    r5 = in[5];
    r6 = in[6];
    r7 = in[7];
    r8 = in[8];
    r9 = in[9];

    m0 = mul32x32_64(r0, r0);
    r0 *= 2;
    m1 = mul32x32_64(r0, r1);
    m2 = mul32x32_64(r0, r2) + mul32x32_64(r1, r1 * 2);
    r1 *= 2;
    m3 = mul32x32_64(r0, r3) + mul32x32_64(r1, r2);
    m4 = mul32x32_64(r0, r4) + mul32x32_64(r1, r3 * 2) + mul32x32_64(r2, r2);
    r2 *= 2;
    m5 = mul32x32_64(r0, r5) + mul32x32_64(r1, r4) + mul32x32_64(r2, r3);
    m6 = mul32x32_64(r0, r6) + mul32x32_64(r1, r5 * 2) + mul32x32_64(r2, r4) +
         mul32x32_64(r3, r3 * 2);
    r3 *= 2;
    m7 = mul32x32_64(r0, r7) + mul32x32_64(r1, r6) + mul32x32_64(r2, r5) + mul32x32_64(r3, r4);
    m8 = mul32x32_64(r0, r8) + mul32x32_64(r1, r7 * 2) + mul32x32_64(r2, r6) +
         mul32x32_64(r3, r5 * 2) + mul32x32_64(r4, r4);
    m9 = mul32x32_64(r0, r9) + mul32x32_64(r1, r8) + mul32x32_64(r2, r7) + mul32x32_64(r3, r6) +
         mul32x32_64(r4, r5 * 2);

    d6 = r6 * 19;
    d7 = r7 * 2 * 19;
    d8 = r8 * 19;
    d9 = r9 * 2 * 19;

    m0 +=
        (mul32x32_64(d9, r1) + mul32x32_64(d8, r2) + mul32x32_64(d7, r3) +
         mul32x32_64(d6, r4 * 2) + mul32x32_64(r5, r5 * 2 * 19));
    m1 +=
        (mul32x32_64(d9, r2 / 2) + mul32x32_64(d8, r3) + mul32x32_64(d7, r4) +
         mul32x32_64(d6, r5 * 2));
    m2 +=
        (mul32x32_64(d9, r3) + mul32x32_64(d8, r4 * 2) + mul32x32_64(d7, r5 * 2) +
         mul32x32_64(d6, r6));
    m3 += (mul32x32_64(d9, r4) + mul32x32_64(d8, r5 * 2) + mul32x32_64(d7, r6));
    m4 += (mul32x32_64(d9, r5 * 2) + mul32x32_64(d8, r6 * 2) + mul32x32_64(d7, r7));
    m5 += (mul32x32_64(d9, r6) + mul32x32_64(d8, r7 * 2));
    m6 += (mul32x32_64(d9, r7 * 2) + mul32x32_64(d8, r8));
    m7 += (mul32x32_64(d9, r8));
    m8 += (mul32x32_64(d9, r9));

    r0 = (uint32_t)m0 & reduce_mask_26;
    c = (m0 >> 26);
    m1 += c;
    r1 = (uint32_t)m1 & reduce_mask_25;
    c = (m1 >> 25);
    m2 += c;
    r2 = (uint32_t)m2 & reduce_mask_26;
    c = (m2 >> 26);
    m3 += c;
    r3 = (uint32_t)m3 & reduce_mask_25;
    c = (m3 >> 25);
    m4 += c;
    r4 = (uint32_t)m4 & reduce_mask_26;
    c = (m4 >> 26);
    m5 += c;
    r5 = (uint32_t)m5 & reduce_mask_25;
    c = (m5 >> 25);
    m6 += c;
    r6 = (uint32_t)m6 & reduce_mask_26;
    c = (m6 >> 26);
    m7 += c;
    r7 = (uint32_t)m7 & reduce_mask_25;
    c = (m7 >> 25);
    m8 += c;
    r8 = (uint32_t)m8 & reduce_mask_26;
    c = (m8 >> 26);
    m9 += c;
    r9 = (uint32_t)m9 & reduce_mask_25;
    p = (uint32_t)(m9 >> 25);
    m0 = r0 + mul32x32_64(p, 19);
    r0 = (uint32_t)m0 & reduce_mask_26;
    p = (uint32_t)(m0 >> 26);
    r1 += p;

    out[0] = r0;
    out[1] = r1;
    out[2] = r2;
    out[3] = r3;
    out[4] = r4;
    out[5] = r5;
    out[6] = r6;
    out[7] = r7;
    out[8] = r8;
    out[9] = r9;
}

/* out = in ^ (2 * count) */
void curve25519_square_times(bignum25519 out, const bignum25519 in, int count) {
    uint32_t r0 = 0, r1 = 0, r2 = 0, r3 = 0, r4 = 0, r5 = 0, r6 = 0, r7 = 0, r8 = 0, r9 = 0;
    uint32_t d6 = 0, d7 = 0, d8 = 0, d9 = 0;
    uint64_t m0 = 0, m1 = 0, m2 = 0, m3 = 0, m4 = 0, m5 = 0, m6 = 0, m7 = 0, m8 = 0, m9 = 0, c = 0;
    uint32_t p = 0;

    r0 = in[0];
    r1 = in[1];
    r2 = in[2];
    r3 = in[3];
    r4 = in[4];
    r5 = in[5];
    r6 = in[6];
    r7 = in[7];
    r8 = in[8];
    r9 = in[9];

    do {
        m0 = mul32x32_64(r0, r0);
        r0 *= 2;
        m1 = mul32x32_64(r0, r1);
        m2 = mul32x32_64(r0, r2) + mul32x32_64(r1, r1 * 2);
        r1 *= 2;
        m3 = mul32x32_64(r0, r3) + mul32x32_64(r1, r2);
        m4 = mul32x32_64(r0, r4) + mul32x32_64(r1, r3 * 2) + mul32x32_64(r2, r2);
        r2 *= 2;
        m5 = mul32x32_64(r0, r5) + mul32x32_64(r1, r4) + mul32x32_64(r2, r3);
        m6 = mul32x32_64(r0, r6) + mul32x32_64(r1, r5 * 2) + mul32x32_64(r2, r4) +
             mul32x32_64(r3, r3 * 2);
        r3 *= 2;
        m7 = mul32x32_64(r0, r7) + mul32x32_64(r1, r6) + mul32x32_64(r2, r5) + mul32x32_64(r3, r4);
        m8 = mul32x32_64(r0, r8) + mul32x32_64(r1, r7 * 2) + mul32x32_64(r2, r6) +
             mul32x32_64(r3, r5 * 2) + mul32x32_64(r4, r4);
        m9 = mul32x32_64(r0, r9) + mul32x32_64(r1, r8) + mul32x32_64(r2, r7) +
             mul32x32_64(r3, r6) + mul32x32_64(r4, r5 * 2);

        d6 = r6 * 19;
        d7 = r7 * 2 * 19;
        d8 = r8 * 19;
        d9 = r9 * 2 * 19;

        m0 +=
            (mul32x32_64(d9, r1) + mul32x32_64(d8, r2) + mul32x32_64(d7, r3) +
             mul32x32_64(d6, r4 * 2) + mul32x32_64(r5, r5 * 2 * 19));
        m1 +=
            (mul32x32_64(d9, r2 / 2) + mul32x32_64(d8, r3) + mul32x32_64(d7, r4) +
             mul32x32_64(d6, r5 * 2));
        m2 +=
            (mul32x32_64(d9, r3) + mul32x32_64(d8, r4 * 2) + mul32x32_64(d7, r5 * 2) +
             mul32x32_64(d6, r6));
        m3 += (mul32x32_64(d9, r4) + mul32x32_64(d8, r5 * 2) + mul32x32_64(d7, r6));
        m4 += (mul32x32_64(d9, r5 * 2) + mul32x32_64(d8, r6 * 2) + mul32x32_64(d7, r7));
        m5 += (mul32x32_64(d9, r6) + mul32x32_64(d8, r7 * 2));
        m6 += (mul32x32_64(d9, r7 * 2) + mul32x32_64(d8, r8));
        m7 += (mul32x32_64(d9, r8));
        m8 += (mul32x32_64(d9, r9));

        r0 = (uint32_t)m0 & reduce_mask_26;
        c = (m0 >> 26);
        m1 += c;
        r1 = (uint32_t)m1 & reduce_mask_25;
        c = (m1 >> 25);
        m2 += c;
        r2 = (uint32_t)m2 & reduce_mask_26;
        c = (m2 >> 26);
        m3 += c;
        r3 = (uint32_t)m3 & reduce_mask_25;
        c = (m3 >> 25);
        m4 += c;
        r4 = (uint32_t)m4 & reduce_mask_26;
        c = (m4 >> 26);
        m5 += c;
        r5 = (uint32_t)m5 & reduce_mask_25;
        c = (m5 >> 25);
        m6 += c;
        r6 = (uint32_t)m6 & reduce_mask_26;
        c = (m6 >> 26);
        m7 += c;
        r7 = (uint32_t)m7 & reduce_mask_25;
        c = (m7 >> 25);
        m8 += c;
        r8 = (uint32_t)m8 & reduce_mask_26;
        c = (m8 >> 26);
        m9 += c;
        r9 = (uint32_t)m9 & reduce_mask_25;
        p = (uint32_t)(m9 >> 25);
        m0 = r0 + mul32x32_64(p, 19);
        r0 = (uint32_t)m0 & reduce_mask_26;
        p = (uint32_t)(m0 >> 26);
        r1 += p;
    } while(--count);

    out[0] = r0;
    out[1] = r1;
    out[2] = r2;
    out[3] = r3;
    out[4] = r4;
    out[5] = r5;
    out[6] = r6;
    out[7] = r7;
    out[8] = r8;
    out[9] = r9;
}

/* Take a little-endian, 32-byte number and expand it into polynomial form */
void curve25519_expand(bignum25519 out, const unsigned char in[32]) {
    uint32_t x0 = 0, x1 = 0, x2 = 0, x3 = 0, x4 = 0, x5 = 0, x6 = 0, x7 = 0;
#define F(s)                                                                                  \
    ((((uint32_t)in[s + 0])) | (((uint32_t)in[s + 1]) << 8) | (((uint32_t)in[s + 2]) << 16) | \
     (((uint32_t)in[s + 3]) << 24))
    x0 = F(0);
    x1 = F(4);
    x2 = F(8);
    x3 = F(12);
    x4 = F(16);
    x5 = F(20);
    x6 = F(24);
    x7 = F(28);
#undef F

    out[0] = (x0)&reduce_mask_26;
    out[1] = ((((uint64_t)x1 << 32) | x0) >> 26) & reduce_mask_25;
    out[2] = ((((uint64_t)x2 << 32) | x1) >> 19) & reduce_mask_26;
    out[3] = ((((uint64_t)x3 << 32) | x2) >> 13) & reduce_mask_25;
    out[4] = ((x3) >> 6) & reduce_mask_26;
    out[5] = (x4)&reduce_mask_25;
    out[6] = ((((uint64_t)x5 << 32) | x4) >> 25) & reduce_mask_26;
    out[7] = ((((uint64_t)x6 << 32) | x5) >> 19) & reduce_mask_25;
    out[8] = ((((uint64_t)x7 << 32) | x6) >> 12) & reduce_mask_26;
    out[9] = ((x7) >> 6) & reduce_mask_25; /* ignore the top bit */
}

/* Take a fully reduced polynomial form number and contract it into a
 * little-endian, 32-byte array
 */
void curve25519_contract(unsigned char out[32], const bignum25519 in) {
    bignum25519 f = {0};
    curve25519_copy(f, in);

#define carry_pass()        \
    f[1] += f[0] >> 26;     \
    f[0] &= reduce_mask_26; \
    f[2] += f[1] >> 25;     \
    f[1] &= reduce_mask_25; \
    f[3] += f[2] >> 26;     \
    f[2] &= reduce_mask_26; \
    f[4] += f[3] >> 25;     \
    f[3] &= reduce_mask_25; \
    f[5] += f[4] >> 26;     \
    f[4] &= reduce_mask_26; \
    f[6] += f[5] >> 25;     \
    f[5] &= reduce_mask_25; \
    f[7] += f[6] >> 26;     \
    f[6] &= reduce_mask_26; \
    f[8] += f[7] >> 25;     \
    f[7] &= reduce_mask_25; \
    f[9] += f[8] >> 26;     \
    f[8] &= reduce_mask_26;

#define carry_pass_full()                   \
    carry_pass() f[0] += 19 * (f[9] >> 25); \
    f[9] &= reduce_mask_25;

#define carry_pass_final() carry_pass() f[9] &= reduce_mask_25;

    carry_pass_full() carry_pass_full()

        /* now t is between 0 and 2^255-1, properly carried. */
        /* case 1: between 0 and 2^255-20. case 2: between 2^255-19 and 2^255-1. */
        f[0] += 19;
    carry_pass_full()

        /* now between 19 and 2^255-1 in both cases, and offset by 19. */
        f[0] += (reduce_mask_26 + 1) - 19;
    f[1] += (reduce_mask_25 + 1) - 1;
    f[2] += (reduce_mask_26 + 1) - 1;
    f[3] += (reduce_mask_25 + 1) - 1;
    f[4] += (reduce_mask_26 + 1) - 1;
    f[5] += (reduce_mask_25 + 1) - 1;
    f[6] += (reduce_mask_26 + 1) - 1;
    f[7] += (reduce_mask_25 + 1) - 1;
    f[8] += (reduce_mask_26 + 1) - 1;
    f[9] += (reduce_mask_25 + 1) - 1;

    /* now between 2^255 and 2^256-20, and offset by 2^255. */
    carry_pass_final()

#undef carry_pass
#undef carry_full
#undef carry_final

        f[1] <<= 2;
    f[2] <<= 3;
    f[3] <<= 5;
    f[4] <<= 6;
    f[6] <<= 1;
    f[7] <<= 3;
    f[8] <<= 4;
    f[9] <<= 6;

#define F(i, s)                                        \
    out[s + 0] |= (unsigned char)(f[i] & 0xff);        \
    out[s + 1] = (unsigned char)((f[i] >> 8) & 0xff);  \
    out[s + 2] = (unsigned char)((f[i] >> 16) & 0xff); \
    out[s + 3] = (unsigned char)((f[i] >> 24) & 0xff);

    out[0] = 0;
    out[16] = 0;
    F(0, 0);
    F(1, 3);
    F(2, 6);
    F(3, 9);
    F(4, 12);
    F(5, 16);
    F(6, 19);
    F(7, 22);
    F(8, 25);
    F(9, 28);
#undef F
}

/* if (iswap) swap(a, b) */
void curve25519_swap_conditional(bignum25519 a, bignum25519 b, uint32_t iswap) {
    const uint32_t swap = (uint32_t)(-(int32_t)iswap);
    uint32_t x0 = 0, x1 = 0, x2 = 0, x3 = 0, x4 = 0, x5 = 0, x6 = 0, x7 = 0, x8 = 0, x9 = 0;

    x0 = swap & (a[0] ^ b[0]);
    a[0] ^= x0;
    b[0] ^= x0;
    x1 = swap & (a[1] ^ b[1]);
    a[1] ^= x1;
    b[1] ^= x1;
    x2 = swap & (a[2] ^ b[2]);
    a[2] ^= x2;
    b[2] ^= x2;
    x3 = swap & (a[3] ^ b[3]);
    a[3] ^= x3;
    b[3] ^= x3;
    x4 = swap & (a[4] ^ b[4]);
    a[4] ^= x4;
    b[4] ^= x4;
    x5 = swap & (a[5] ^ b[5]);
    a[5] ^= x5;
    b[5] ^= x5;
    x6 = swap & (a[6] ^ b[6]);
    a[6] ^= x6;
    b[6] ^= x6;
    x7 = swap & (a[7] ^ b[7]);
    a[7] ^= x7;
    b[7] ^= x7;
    x8 = swap & (a[8] ^ b[8]);
    a[8] ^= x8;
    b[8] ^= x8;
    x9 = swap & (a[9] ^ b[9]);
    a[9] ^= x9;
    b[9] ^= x9;
}

void curve25519_set(bignum25519 r, uint32_t x) {
    r[0] = x & reduce_mask_26;
    x >>= 26;
    r[1] = x & reduce_mask_25;
    r[2] = 0;
    r[3] = 0;
    r[4] = 0;
    r[5] = 0;
    r[6] = 0;
    r[7] = 0;
    r[8] = 0;
    r[9] = 0;
}

void curve25519_set_d(bignum25519 r) {
    curve25519_copy(r, ge25519_ecd);
}

void curve25519_set_2d(bignum25519 r) {
    curve25519_copy(r, ge25519_ec2d);
}

void curve25519_set_sqrtneg1(bignum25519 r) {
    curve25519_copy(r, ge25519_sqrtneg1);
}

int curve25519_isnegative(const bignum25519 f) {
    unsigned char s[32] = {0};
    curve25519_contract(s, f);
    return s[0] & 1;
}

int curve25519_isnonzero(const bignum25519 f) {
    unsigned char s[32] = {0};
    curve25519_contract(s, f);
    return ((((int)(s[0] | s[1] | s[2] | s[3] | s[4] | s[5] | s[6] | s[7] | s[8] | s[9] | s[10] | s[11] | s[12] | s[13] | s[14] | s[15] | s[16] | s[17] | s[18] | s[19] | s[20] | s[21] | s[22] | s[23] | s[24] | s[25] | s[26] | s[27] | s[28] | s[29] | s[30] | s[31]) -
              1) >>
             8) +
            1) &
           0x1;
}

void curve25519_reduce(bignum25519 out, const bignum25519 in) {
    uint32_t c = 0;
    out[0] = in[0];
    c = (out[0] >> 26);
    out[0] &= reduce_mask_26;
    out[1] = in[1] + c;
    c = (out[1] >> 25);
    out[1] &= reduce_mask_25;
    out[2] = in[2] + c;
    c = (out[2] >> 26);
    out[2] &= reduce_mask_26;
    out[3] = in[3] + c;
    c = (out[3] >> 25);
    out[3] &= reduce_mask_25;
    out[4] = in[4] + c;
    c = (out[4] >> 26);
    out[4] &= reduce_mask_26;
    out[5] = in[5] + c;
    c = (out[5] >> 25);
    out[5] &= reduce_mask_25;
    out[6] = in[6] + c;
    c = (out[6] >> 26);
    out[6] &= reduce_mask_26;
    out[7] = in[7] + c;
    c = (out[7] >> 25);
    out[7] &= reduce_mask_25;
    out[8] = in[8] + c;
    c = (out[8] >> 26);
    out[8] &= reduce_mask_26;
    out[9] = in[9] + c;
    c = (out[9] >> 25);
    out[9] &= reduce_mask_25;
    out[0] += 19 * c;
}

void curve25519_divpowm1(bignum25519 r, const bignum25519 u, const bignum25519 v) {
    bignum25519 v3 = {0}, uv7 = {0}, t0 = {0}, t1 = {0}, t2 = {0};
    int i = 0;

    curve25519_square(v3, v);
    curve25519_mul(v3, v3, v); /* v3 = v^3 */
    curve25519_square(uv7, v3);
    curve25519_mul(uv7, uv7, v);
    curve25519_mul(uv7, uv7, u); /* uv7 = uv^7 */

    /*fe_pow22523(uv7, uv7);*/
    /* From fe_pow22523.c */

    curve25519_square(t0, uv7);
    curve25519_square(t1, t0);
    curve25519_square(t1, t1);
    curve25519_mul(t1, uv7, t1);
    curve25519_mul(t0, t0, t1);
    curve25519_square(t0, t0);
    curve25519_mul(t0, t1, t0);
    curve25519_square(t1, t0);
    for(i = 0; i < 4; ++i) {
        curve25519_square(t1, t1);
    }
    curve25519_mul(t0, t1, t0);
    curve25519_square(t1, t0);
    for(i = 0; i < 9; ++i) {
        curve25519_square(t1, t1);
    }
    curve25519_mul(t1, t1, t0);
    curve25519_square(t2, t1);
    for(i = 0; i < 19; ++i) {
        curve25519_square(t2, t2);
    }
    curve25519_mul(t1, t2, t1);
    for(i = 0; i < 10; ++i) {
        curve25519_square(t1, t1);
    }
    curve25519_mul(t0, t1, t0);
    curve25519_square(t1, t0);
    for(i = 0; i < 49; ++i) {
        curve25519_square(t1, t1);
    }
    curve25519_mul(t1, t1, t0);
    curve25519_square(t2, t1);
    for(i = 0; i < 99; ++i) {
        curve25519_square(t2, t2);
    }
    curve25519_mul(t1, t2, t1);
    for(i = 0; i < 50; ++i) {
        curve25519_square(t1, t1);
    }
    curve25519_mul(t0, t1, t0);
    curve25519_square(t0, t0);
    curve25519_square(t0, t0);
    curve25519_mul(t0, t0, uv7);

    /* End fe_pow22523.c */
    /* t0 = (uv^7)^((q-5)/8) */
    curve25519_mul(t0, t0, v3);
    curve25519_mul(r, t0, u); /* u^(m+1)v^(-(m+1)) */
}

void curve25519_expand_reduce(bignum25519 out, const unsigned char in[32]) {
    uint32_t x0 = 0, x1 = 0, x2 = 0, x3 = 0, x4 = 0, x5 = 0, x6 = 0, x7 = 0;
#define F(s)                                                                                  \
    ((((uint32_t)in[s + 0])) | (((uint32_t)in[s + 1]) << 8) | (((uint32_t)in[s + 2]) << 16) | \
     (((uint32_t)in[s + 3]) << 24))
    x0 = F(0);
    x1 = F(4);
    x2 = F(8);
    x3 = F(12);
    x4 = F(16);
    x5 = F(20);
    x6 = F(24);
    x7 = F(28);
#undef F

    out[0] = (x0)&reduce_mask_26;
    out[1] = ((((uint64_t)x1 << 32) | x0) >> 26) & reduce_mask_25;
    out[2] = ((((uint64_t)x2 << 32) | x1) >> 19) & reduce_mask_26;
    out[3] = ((((uint64_t)x3 << 32) | x2) >> 13) & reduce_mask_25;
    out[4] = ((x3) >> 6) & reduce_mask_26;
    out[5] = (x4)&reduce_mask_25;
    out[6] = ((((uint64_t)x5 << 32) | x4) >> 25) & reduce_mask_26;
    out[7] = ((((uint64_t)x6 << 32) | x5) >> 19) & reduce_mask_25;
    out[8] = ((((uint64_t)x7 << 32) | x6) >> 12) & reduce_mask_26;
    out[9] = ((x7) >> 6); // & reduce_mask_25; /* ignore the top bit */
    out[0] += 19 * (out[9] >> 25);
    out[9] &= reduce_mask_25;
}
